1. Field of Invention
The present invention relates to apparatuses and methods for monitoring, measuring, or analyzing the volumetric expansion or contraction (“swell”) of a solid sample.
2. Description of Prior Art
Borehole instability in clay-rich rocks such as shaly sandstones, mudstones and shales is regarded as the prime technical problem area in oil and gas well drilling, and is one of the principal causes of trouble during the drilling process. It has been noted that shales make up over 75% of drilled formations and cause over 90% of wellbore stability problems, many of which result in stuck pipe. Thus, there is a great need for methods and apparatuses to accurately and quantitatively measure the hydration and swelling behavior of shales when exposed to different drilling fluids. Understanding and controlling these behaviors can be vital to the stability of the wellbore.
U.S. Pat. No. 6,247,358 describes a mechanism for the evaluation of shale reactivity. The mechanism requires a sample collection method that is inflexible, difficult to perform, requires a specific hardware mechanism and operation method for sample collection and storage, and is highly specific to only one type of shale testing. These problems prevent the design outlined in the patent from being reliably used to test samples collected under any conditions other than those specified therein.
U.S. Pat. No. 6,247,358 and U.S. Pat. No. 5,275,063 both describe a testing method in which a shale sample is confined within a pressure chamber and exposed to testing fluid under conditions of temperature and constant triaxial pressure. As the sample expands or contracts, pressure is applied to counter the change, preventing the sample from actually expanding or contracting. This methodology addresses only one specific instance of shale reactivity, in which the sample is collected from a core taken from a wellbore. It requires testing apparatus which is complex and expensive to configure, operate and maintain. Thus there is a need for a testing mechanism which can test sample reactivity using a simpler, more flexible and robust mechanism, and without a need for a specific configuration, origin, or substance of sample.
It is an object of this invention to provide a means for measuring the hydration and/or swelling behavior of solid sample material under varying and controllable conditions of temperature and pressure.
It is a further object of this invention to provide a means for testing said solid sample material while either eliminating the need for pressurization fluid, or keeping the exposure of sample material to pressurization fluid to a minimum.
It is a further object of this invention to provide a means for automatically and digitally tracking and recording changes in sample swelling.
It is another object of this invention to provide a specific swelling measurement device which requires substantially less maintenance work than other designs yet meets industry standards of accuracy, reliability, durability, dependability, and ease of cleaning.